The present invention relates to the field of amplifiers, and, in particular, to an auto-zeroed amplifier that is suitable for low frequency applications such as a voltage regulator. The amplifier provides reduced output ripple in voltage regulator applications.
An operational amplifier has inherent mismatches that cause an input referred error or offset voltage. A zero differential input voltage will produce a non-zero output because of the mismatches. One solution to this problem is to auto-zero the amplifier using a sampling procedure.
An auto-zero amplifier has two separate phases, an auto-zero phase and an amplifier phase. During the auto-zero phase, the differential input voltages of the operational amplifier is held at a voltage of approximately zero and an output voltage is produced. The output voltage that is produced in the auto-zero phase is stored using capacitors. During the amplification phase, the stored offset voltage is used to correct for the offset on the input to the amplifier.